Question Info

Doing this will not get your gamerscore reset. Yes it is cheap but they won't take action against the accounts that do this. Games have had achievements like this for a while now and people have always changed the clocks to get the achievements. It will
be noticeable because there won't be a time stamp so you'll be able to tell who got it legit.

It won't get your gamer score reset. But it is cheating. A little. But the only person you are cheating is yourself. If you want to go through games getting your score up the easy way then go ahead. No one will mind. Except maybe....you.